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Gulf Stream warm‐core rings (WCRs) impinging onto the Mid‐Atlantic Bight (MAB) shelf edge can induce substantial water exchange between the shelf and slope seas. Combining satellite imagery and idealized ocean models, this study investigates the long‐neglected influence of submarine canyons on the WCR impingement process. Satellite images show onshore intrusion of the WCR water concentrated near the MAB shelf‐break canyons, indicating canyon‐induced enhancement of cross‐shelf exchange. Model simulations of the ring‐canyon interaction qualitatively reproduce the observed pattern and show greatly enhanced vertical motions and cross‐shelf transport in a canyon. The ring‐induced transient flow in a canyon resolved by the model is consistent with the three‐dimensional canyon circulation driven by ambient along‐slope steady flows as depicted in the literature. Cross‐isobath flows occur over both canyon slopes with a strong upwelling onshore flow over the slope upstream to the coastal‐trapped wave propagation (the upwave slope) and a weak downwelling offshore flow over the downwave slope. To conserve potential vorticity, a subsurface‐intensified cyclonic eddy is formed inside the canyon, which interacts with the sloping bottom and enhances the upwelling onshore flow over the upwave slope. The upwelled deep ring water is transported either back offshore by the ring‐edge current on the upwave side of the canyon or across the canyon onto the downwave shelf forming a localized bulge pattern. While the former is an ephemeral onshore transport process, the latter represents a more sustained onshore transport of the ring water, both of which have major implication for ecosystem dynamics at the shelf edge. Plain Language Summary: Waters on the Mid‐Atlantic Bight continental shelf and in the neighboring deep ocean have dramatically different physical and biological properties. Warm vortices with diameters of 100–150 km, so‐called warm‐core rings, broken off the unstable Gulf Stream can migrate in the deep ocean and interact with the shallower shelf edge resulting in water exchange between the shelf and the deep ocean. This study investigates the influence of shelf‐edge submarine canyons on the ring‐induced cross‐shelf water exchange. Satellite‐measured sea surface temperature indicates that shelf‐edge canyons enhance onshore intrusion of the offshore ring water onto the continental shelf. Computer models with simplified canyon topography and warm‐core rings qualitatively reproduce the satellite‐observed ring‐canyon interaction, and confirm that canyons can enhance cross‐shelf water exchange during the impingement of a warm‐core ring onto the shelf edge. The models also reveal a complex three‐dimensional circulation pattern inside the canyon, including a confined deep eddy and a strong upward flow on one of the canyon side slopes. The latter can transport a substantial amount of nutrient‐rich deep offshore water into the surface layer on both sides of the shelf edge and thus stimulate biological productivity on the continental shelf and also in the deep ocean. Key Points: Satellite imagery shows localized onshore intrusion of Gulf Stream warm‐core ring water at the Mid‐Atlantic Bight shelf‐break canyonsIdealized model simulations reveal the formation of a subsurface eddy inside the canyon when a warm‐core ring impinges onto the canyonInteraction of the subsurface eddy with the canyon topography enhances intrusion of the warm‐core ring water onto the continental shelf [ABSTRACT FROM AUTHOR]

Effects of the assimilation of relative humidity (RH) reproduced from dropsonde data from the Tropical cyclones‐Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts (T‐PARCII) campaign and Himawari‐8 satellite data on the simulation of Typhoon Lan (2017) were investigated herein using a weather research and forecasting model. The lateral boundary and initial conditions were obtained from Global Forecast System (GFS) forecast data. Four experiments varying from the initial vortex, assimilation of the reproduced RH (ARH), and ocean model (OCEAN, three‐dimensional Price‐Weller‐Pinkel upper‐ocean circulation model) activation were conducted for 42 h to evaluate tropical cyclone (TC) forecast performance: the GFS experiment and dynamical initialization (DI) experiments such as DI, DI‐OCEAN, and DI‐ARH‐OCEAN, respectively. All track forecast errors were less than 100 km until landfall, that is, up to 36 h. TC intensity forecasts such as the minimum sea‐level pressure and maximum surface wind speed were slightly improved in DI‐related experiments compared to the GFS experiment. The DI‐ARH‐OCEAN experiment, in particular, demonstrated improvements in both TC forecasts and convective areas. The ocean‐coupled experiments yielded significant sea surface temperature cooling in the rear‐right quadrant of TC, forming a stable boundary layer that could suppress the convective activity, particularly in the lower troposphere. These findings support that compared to the original DI method, ARH could improve initial conditions, resulting in more accurate TC forecasts. Furthermore, it may argue the necessity and urgency of regular aircraft surveillance of TCs in the western North Pacific area. Key Points: Relative humidity can be reproduced using in situ aircraft and remote‐sensing dataThe dynamical initialization method with the assimilation of reproduced relative humidity can further improve tropical cyclone forecastsThe ocean‐coupled experiment shows that the storm‐induced SST cooling can weaken tropical cyclone intensity [ABSTRACT FROM AUTHOR]

Four previously identified patterns of meso‐scale cloud organization in the trades — called Sugar, Gravel, Flowers, and Fish — are studied using long‐term records of ground‐based measurements, satellite observations and reanalyzes. A deep neural network trained to detect these patterns is applied to satellite imagery to identify periods during which a particular pattern is observed over the Barbados Cloud Observatory. Surface‐based remote sensing at the observatory is composited and shows that the patterns can be distinguished by differences in cloud geometry. Variations in total cloudiness among the patterns are dominated by variations in cloud‐top cloudiness. Cloud amount near cloud base varies little. Each pattern is associated with a distinct atmospheric environment whose characteristics are traced back to origins that are not solely within the trades. Sugar air‐masses are characterized by weak winds and of tropical origin. Fish are driven by convergence lines originating from synoptical disturbances. Gravel and Flowers are most native to the trades, but distinguish themselves with slightly stronger winds and stronger subsidence in the first case and greater stability in the latter. The patterns with the higher cloud amounts and more negative cloud‐radiative effects, Flowers and Fish, are selected by conditions expected to occur less frequently with greenhouse warming. Key Points: Meso‐scale patterns of trade‐wind clouds are identified with a neural network and characterized based on observationsThe four analyzed patterns distinguish themselves by stratiform cloudiness and less by cloudiness at the lifting condensation levelTwo patterns are imprinted by tropical, respectively extra‐tropical intrusions [ABSTRACT FROM AUTHOR]

A contemporary seasonal forecasting system is used to study the impacts of a volcanic sulfate injection into the stratosphere on the seasonal forecasts for surface temperatures, the El Niño Southern Oscillation (ENSO), and precipitation. The focus is a case study of the June 1991 eruption of Mt. Pinatubo, Philippines and the period from July 1991 to February 1992. Version 2 of the Goddard Earth Observing System (GEOS) subseasonal‐to‐seasonal (S2S) forecasting system is used in this study. GEOS‐S2S includes the GOddard Chemistry, Aerosols, Radiation and Transport (GOCART) aerosol module, which allows to prognostically simulate aerosol distributions. GOCART is coupled to the radiation and cloud modules to include the impact of the eruption on forecasted radiation and precipitation. The coupled GEOS‐S2S system was initialized in May 1991 with fields based on observations to produce ten‐member 9‐month forecasts with and without the volcanic sulfur injection. The results of these ensemble experiments demonstrate that including Mt. Pinatubo in seasonal forecasts would improve the forecasts of the 1991–1992 global mean temperature and precipitation but worsen the forecast of ENSO by strengthening of El Niño beyond what showed in observations. Most significant changes in the forecasts of temperatures and precipitation are limited to the tropics. The only land area where the inclusion of Pinatubo significantly lowered the forecasted precipitation is tropical Africa. Key Points: The inclusion of the 1991 Pinatubo eruption improves the skill of GEOS‐S2S forecasting hemispheric temperature and precipitation ratesThe inclusion of Pinatubo strengthens the forecasted El Niño beyond observationsPinatubo does not significantly modify the forecasts of temperatures and precipitation in most extratropical regions [ABSTRACT FROM AUTHOR]

This study investigates the occurrence of mixed‐phase clouds (MPC, i.e., cloud layers containing both liquid and ice water at sub‐freezing temperatures) over the Southern Ocean (SO) using space‐ and surface‐based lidar and radar observations. The occurrence of supercooled clouds is dominated by geometrically thin (<1 km) layers that rarely contain ice. We diagnose layers that are geometrically thicker than 1 km to contain ice ~65% and ~4% of the time from below by surface remote sensors and from above by orbiting remote sensors, respectively. We examine the discrepancy in MPC occurrence statistics as diagnosed from below and above the cloud layer. From above, we find that MPC occurrence has a gradient associated with the Antarctic Polar Front near 55°S with a rare occurrence of satellite‐derived MPC south of that latitude. In contrast, surface sensors find ice in 33% of supercooled liquid water layers. We infer using observing system simulation experiments and data analysis that space‐based lidar cannot identify the occurrence of MPC except when secondary ice‐forming processes operate in convection that is, sufficiently strong to loft ice crystals to cloud tops. We conclude that the CALIPSO phase statistics of MPC have a severe low bias in MPC occurrence. Based on surface‐based statistics in the SO, we present a parameterization of the frequency of MPC as a function of cloud top temperature that differs substantially from that used in recent climate model simulations. Plain Language Summary: The existence of snow in predominantly liquid clouds has important implications for the amount of sunlight absorbed mostly at the sea surface over the high latitude oceans. Particularly over the Southern Ocean, where satellite measurements suggest that ice concentrations are low, knowledge of how often clouds are snowing has critical climate implications. Observations from the surface have high fidelity in identifying snow below cold clouds. We use new measurements collected from Australian research vessels to establish an accurate survey of snow occurrence. We find that the occurrence of snow below cold clouds is much higher from ship observations than inferred from satellite. We explore reasons for this discrepancy and settle on an explanation that the low concentrations of ice‐nucleating aerosol particles result in low concentrations of ice particles except where convective motions are strong enough to create ice particles spontaneously by freezing large drops. We provide a simple temperature‐based parameterization of snow occurrence using surface‐based measurements for atmospheric models to use. Key Points: Lidar observations from above cloud layers significantly undercount the occurrence of mixed phase clouds over the Southern Ocean (SO)A latitudinal gradient in mixed‐phase clouds is found associated with the Antarctic Polar Front of the Antarctic Circumpolar CurrentCurrent parameterizations that modify the phase detrainment temperature of shallow convection are not supported by observations. An alternate parameterization developed from SO surface data is suggested [ABSTRACT FROM AUTHOR]

The suspended particulate matter (SPM) concentration (unit: mg l-1) in surface waters is an essential measure of water quality and clarity. Satellite remote sensing provides a powerful tool to derive the SPM with synoptic and repeat coverage. In this study, we developed a new global SPM algorithm utilizing the remote sensing reflectance (Rrs(λ)) at near-infrared (NIR), red, green, and blue bands (NIR-RGB) as input. The evaluations showed that the NIR-RGB algorithm could predict SPM with the median absolute percentage difference of ~35%-39% over a wide range from ~0.01 to >2,000 mg l-1. The uncertainty is smaller (29%-37%) for turbid waters where Rrs(671) ≥ 0.0012 sr-1 and slightly higher (41%-44%) for clear waters where Rrs(671) < 0.0012 mg l-1. The algorithm was implemented with the global Rrs(λ) data from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. We provided a brief characterization of the spatial distribution and temporal trends of the SPM products in global waters based on the monthly SPM composites. Case studies of the SPM time series in coastal and inland waters suggest that the satellite SPM estimations registered spatial and seasonal variation and episodic events in regional scales as well. The VIIRS-generated global SPM maps provide a valuable addition to the existing ocean color products for environmental and climate applications. [ABSTRACT FROM AUTHOR]

Baroclinic seamount-trapped waves are thought to influence their surrounding ecosystem; however, trapped waves are not well-studied in near-equatorial settings, where stratification is strong and Burger numbers (...) are large. Motivated by observations, we use daily output (2005-2009) from the global Parallel Ocean Program Model (POP) to examine topographically trapped baroclinic waves around the Seychelles Plateau (S > 400) in the tropical Indian Ocean. These trapped waves are associated with velocity and temperature oscillations at periods of 15-16 days, similar to the dominant period of some equatorial Yanai waves. Energy flux maps using POP output suggest that quasi-biweekly equatorial Yanai waves excite trapped waves on the western and south-western flanks of the Seychelles Plateau, near the surface. The anticyclonic energy flux associated with the trapped wave extends vertically throughout the water column and around most of the plateau circumference, diminishing on the eastern flank of the plateau. This work highlights the role that equatorial planetary waves and trapped waves play in facilitating energy redistribution, dissipation, and mixing in the tropical ocean. [ABSTRACT FROM AUTHOR]

Turbulence or turbulence-like phenomena are ubiquitous in nature, often showing a power-law behavior of the fluctuations in either spatial or temporal domains. This power-law behavior is due to interactions among different scales of motion, and to the absence of characteristic scale. In this work, we consider the multiscale dynamics of China France Oceanography SATellite (CFOSAT) data as atmospheric and oceanic quantities influenced by turbulence. Fourier power spectra were estimated for the data provided by the CFOSAT via the Wiener-Khinchine theorem to extract multiscale information for both wind speed (WS) and significant wave height (Hs). The WS data were collected from December 18, 2018 to August 31, 2020, and the Hs data from July 29, 2019 to August 31, 2020. Fourier power spectra for both WS and Hs exhibit power-law features in the ranges of 100-3,000 km with a scaling exponent β varying from 5/3 to 3. The global distributions and seasonal variations of β for both WS and Hs have also been considered. The results show that due to the energetic convective activities in the low-latitude zones, the scaling exponents β in these regions are closer to the value of 5/3. Concerning the seasonal variations, for most regions, the scaling exponents in winter are larger than those in summer for WS. The seasonal variations of β in low-latitudes are stronger than those in the mid-latitudes. Our preliminary results enrich the fundamental knowledge of ocean surface processes and also provide a benchmark for either oceanic or atmospheric models. [ABSTRACT FROM AUTHOR]

The continuous uplift and evolution of the Qinghai‐Tibet Plateau region (TPR) represents one of the most important Cenozoic geological events on Earth. The deformation mechanism of the lithosphere in the TPR is still under debate. Relevant viewpoints can be informed by investigations of the lithospheric density structure in the Qinghai‐Tibet Plateau and surrounding regions (TP‐SRs). Considering investigating the fine‐scale lithospheric density structure of the large‐scale areas, the GOCE satellite data covering entire TP‐SRs are used in this study. GOCE gravity gradient data are first subjected to several corrections. Then, based on gravity gradient curvature (SI) calculation complemented with the preconditioned conjugate gradient algorithm, the distribution of SI and the lithospheric density structure at depths of 0–80 km in TP‐SRs are obtained. The effects of temperature differences and material composition on the lithospheric density distribution are further distinguished. The results show that in the crust, the density anomalies in the TPR are blocked by the surrounding hard blocks. In the upper mantle, the distribution of the density anomalies in the TPR is predominantly affected by the northward subduction of the Indian Plate and the high heat flux environment. The Longmen Shan Thrust Belt is found to have penetrated the lower crust but has not reached the depth of the upper mantle. The density anomalies in the basins on the northern side of the TPR exhibit features indicative of independent stable blocks. Key Points: Gravity gradient inversion coupled with curvature calculation are used to investigate the fine‐scale density structure of the lithosphereThe effects of temperature differences and material composition on the lithospheric density distribution are further distinguishedThe anomalous gravity gradient effect resulting from the uncertainty of the Moho layer depth is considered and assessed [ABSTRACT FROM AUTHOR]

Mechanisms controlling the heat budget of the North Sea are investigated based on a combination of satellite sea surface temperature measurements and numerical model simulations. Lateral heat fluxes across the shelf edge and into the Baltic Sea as well as vertical ocean‐atmosphere heat exchange are considered. A 3‐D variational (3DVAR) data assimilation (DA) scheme is applied, which contains assumed model error correlations that depend on the mixed layer depth derived from a coupled circulation/ocean wave model. The analysis balances pressure gradients introduced by temperature modifications. Significant hydrodynamic model response to DA was found, which should be considered in the heat budget estimations. The observed change of the current velocity field decreases the lateral advective volume/heat exchanges between the North Sea and the Atlantic, yielding an increased heat flux from the Atlantic into the North Sea and more heat flux from the sea to the atmosphere. The largest DA impact on volume/heat transport is in the Norwegian Channel, where the dominant process is Eulerian transport, followed by tidal pumping and wind pumping. Further analysis reveals an acceleration of the along‐shelf current at the northern edge of the North Sea, a decrease in the horizontal pressure gradient from the Atlantic to the North Sea, and a reduction of the Eulerian transport of volume/heat outward the North Sea. Furthermore, the coupling between the circulation model and the wave model has significant impacts on lateral heat advection in the DA run, which is due to the wave impact on the mixed layer depth. Plain Language Summary: Seawater temperature simulations are important for climate change research, fishery management, coastline protection, ecological balance maintenance, and weather predictions. To improve the seawater temperature prediction capability, a data assimilation (DA) scheme is often applied to combine data from measurements, such as from satellites, buoys, and ships, with data provided by climate models that consider circulation, wave, atmosphere, and ice components. For decades, various DA methods have been developed with a focus on implementing sophisticated mathematical techniques. However, few studies have focused on the impacts of DA on physical processes and the secondary effects of DA. We used a model and satellite data to investigate the impacts of sea surface temperature (SST) assimilations on the volume and heat budgets over the North Sea. We found that DA improved SST modeling, thereby modifying the volume and heat budgets between the North Sea and the Atlantic. The largest change occurs at the Norwegian Channel, where the total water/heat transport from the North Sea outward is reduced. Moreover, SST assimilation also changes the air‐sea heat exchange. This study improves our understanding of the relations between model physics and DA. Key Points: Even with balanced pressure gradients there is a significant response of the three‐dimensional model circulation to sea surface temperature (SST) assimilation in the North SeaVolume transports through the Norwegian Channel are modified by SST assimilation leading to changes in lateral heat advectionMechanisms controlling the heat budget of the North Sea are different at west, north, and east boundaries [ABSTRACT FROM AUTHOR]

Eddies in the Western Arctic play an important role in transporting heat, salt, and biogeochemical tracers across the continental shelf and within the deep basins. However, comprehensive observations of the regional and temporal variability of the eddy field characteristics are difficult to obtain remotely due to the presence of sea ice, and the available in situ observations remain relatively sparse. Nonetheless, with continuing global warming, increasingly large areas of the Arctic Ocean become seasonally ice‐free and can be observed with remote sensing. Here, we use satellite altimetry data acquired between 1993 and 2018 over the seasonally ice‐free Western Arctic Ocean to detect the signatures and hot spots of large mesoscale eddies, validating their detection method using independent optical and infrared satellite observations. The altimetry measurements were most frequent from July to October, revealing signatures of over 2000 individual eddies that were roughly equally partitioned between cyclones and anticyclones, with radii between 20 and 60 km and characteristic orbital velocities of about 0.05–0.4 m/s. A maximum number of eddies were detected in October in the Beaufort Sea and in November in the Chukchi Sea. The interannual variability of eddies in the Beaufort Sea is correlated with variations of intensity and freshwater content in the Beaufort Gyre. Using the regional eddy statistics, we discuss the potential eddy formation mechanisms over the key regions of their observations in the Amundsen Gulf, the area adjacent to the Mackenzie River mouth, the western part of the Beaufort Sea, and the Chukchi Sea. Plain Language Summary: Ocean dynamics at scales greater than about 10 km are dominated by energetic eddies but are hard to observe in the Arctic Ocean because of sea ice. Eddies affect the horizontal exchange of heat, salt, and nutrients, changing the thermohaline structure and ecosystem of the Arctic Ocean. Here, we present the first comprehensive study of eddy statistics in ice‐free regions of the western Arctic Ocean using frequent satellite observations of sea surface height from 1993 to 2018. Using an automated detection method that we validated with satellite optical images, we quantify the eddies' pathways, shape, and dynamics, and their spatial and interannual variability. Due to the comprehensive spatial coverage of altimetry satellites, we were able to identify hot spots of eddy generation in the study region: the entrance to the Amundsen Gulf, the area near the Mackenzie River mouth, the western part of the Beaufort Sea, and the Chukchi Sea. Key Points: Altimetry data reveals that large mesoscale eddies are abundant in the seasonally ice‐free Western Arctic OceanThe eddy hot spots in the study region are the Amundsen Gulf, Mackenzie River mouth, the western Beaufort Sea, and the Chukchi SeaThe interannual variability of eddy number and intensity is mainly driven by the intensity of the anticyclonic Beaufort Gyre [ABSTRACT FROM AUTHOR]

Satellite altimetry data have revealed a global mean sea level rise of 3.1 mm/yr since 1993 with large regional sea level variability. These remote data highlight complex structures especially in strongly eddying regions. A recent study showed that over 38% of the global ocean area, the chaotic variability may hinder the attribution to the atmospheric forcing of regional sea level trends from 1993 to 2015. This study aims to complement this work by focusing on the atmospherically forced and chaotic interannual variability of regional sea level and its components. At interannual time scales, variability can hamper the detection of regional sea level trends. A global 1/4° ocean/sea-ice 50-member ensemble simulation is analyzed to disentangle the imprints of the atmospheric forcing and of the chaotic ocean variability on the interannual variability of regional sea level and of its steric and manometric components over 1993--2015. The atmospherically forced and chaotic interannual variabilities of sea level mainly have a steric origin, except in coastal areas. The chaotic part of the interannual variability of sea level and its components is stronger in the Pacific and Atlantic Oceans than in the Indian Ocean. The chaotic part of the interannual variance of sea level and of its steric component exceeds 20% over 48% of the global ocean area; this fractional area reduces to 26% for the manometric component. These results confirm the substantial imprint of the chaotic interannual variability on sea level components, questioning in several regions the attribution of their observed evolution to atmospheric causes. [ABSTRACT FROM AUTHOR]

The meridional overturning circulation (MOC) is a major driver in global redistribution of heat, which modulates global climate and weather. Altimeter sea surface height measurements and in situ hydrographic data are combined in this work to derive monthly synthetic temperature and salinity (T/S) profiles along zonal transbasin sections in both the North (26.5°N) and South (20°S, 25°S, 30°S, and 35°S) Atlantic Ocean since 1993, which are then used to estimate the MOC and meridional heat transport (MHT). Consistent with previous studies, the results indicate that the MHT is highly correlated with the MOC at all five latitudes. At 26.5°N the mean MHT from synthetic profiles (1.09 ± 0.21 PW) is slightly lower than that from the RAPID-MOCHA-WBTS array (1.20 ± 0.28 PW), but their interannual variabilities show good agreements. Both the geostrophic and Ekman components contribute significantly to the MHT variability, with the geostrophic component dominating during 1993--2004 and the Ekman component dominating during 2005--2014. In the South Atlantic, the MHT seasonal cycle strengthens southward from 20°S to 34.5°S. On interannual time scale, the MHT at 20°S and 25°S experiences larger variations than that at 30°S and 34.5°S, in part due to the fact that the geostrophic and Ekman components work together to strengthen the MHT changes, while they tend to work against each other at 30°S and 34.5°S. Results shown here suggest that integrating data from different observing platforms provides better means to estimate the MOC and MHT in near real time. [ABSTRACT FROM AUTHOR]

Observations of the China-France oceanography satellite are used to investigate the wave distribution's asymmetry during tropical cyclone (TC) from August 2019 to August 2020. The spatial distribution of TC waves is analyzed based on an individual case, six ocean basins, and TCs categories. A study of super typhoon Hagibis shows that the highest significant wave height (SWH) appears on the typhoon track's right side. Further analysis reveals that the highest SWH is located on the right (left) side of TC tracks in the Northern Hemisphere (Southern Hemisphere). In the Western North Pacific, North Atlantic, Eastern North Pacific, and North Indian Ocean, the highest SWH is on the right side of TCs of 251, 260, 130, and 118 km, respectively. In the South Pacific and South Indian Ocean, the highest SWH is on the left side of 70 and 128 km. According to the TC categories, the largest (smallest) departure happens during the weakest (strongest) TC. The intensifying of TC favors the wavefield's growth and reduces the asymmetry of the wave height's distribution. Both the asymmetric wind fields and the land's orographic effects impact the TC wave's distribution. In the Eastern North Pacific, the TC wind is the weakest, but the departure is not the smallest, probably due to the left continent bounding the wave energy's propagation. [ABSTRACT FROM AUTHOR]

Water turbidity is an important indicator of water quality, which regulates primary production by changing the light field in the water column. Thus, monitoring the spatial and temporal variations in water turbidity is environmentally and biologically important. In this study, nine commonly used spectral index algorithms were tuned using in situ data collected from two field surveys in the Pearl River Estuary of China, and the spectral ratios between the red and green bands (i.e., Rrs(678)/Rrs (531) and Rrs (645)/Rrs(555) were selected as the optimal indicator to estimate water turbidity in this region. A long-term environmental data record of water turbidity was established for the Pearl River Estuary by applying the proposed algorithm to MODIS/Aqua data covering the estuary from 2003 to 2019. Water turbidity in the Pearl River Estuary has significantly decreased at a rate of 0.11 nephelometric turbidity units (NTU) per year (R² = 0.84, p < 0.01). The decline in water turbidity is linked with sea-level rise in this area. Sea-level rise may cause the longitudinal and lateral landward retreat of estuarine turbidity maxima (ETMs), directly contributing to the decline in water turbidity. Further, the sea-level rise and the decline in water turbidity in the Pearl River Estuary are also two effects resulting from similar processes, such as urbanization. A high degree of correlation was observed between the water turbidity and salinity, which could facilitate promising monitoring of the increasingly severe saltwater intrusions in this region. [ABSTRACT FROM AUTHOR]

This study investigates the satellite altimeter-derived ocean parameters from Joint Altimetry Satellite Oceanography Network (Jason)-2 and Jason-3 response to the coincident wind speed at 10 m from sea surface (U10) from Meteorological Operational (MetOp)-A and MetOp-B satellite scatterometers inside the tropical cyclone environment. The high wind speed regime and rainy condition inside the tropical cyclone have reduced the U10 accuracy and thus, would benefit from more ocean related parameters to be considered. The altimeter Ku-band backscatter and significant wave height are commonly used to estimate extreme U10 but still show significant error in rainy tropical cyclone. New U10 models incorporating several Jasons derived ocean parameters (including brightness temperatures and water content) were designed by the multiple linear regression and artificial neural network techniques. Parameter analysis indicated that the C-band backscatter outperforms the Ku-band counterpart in relation to U10 inside the tropical cyclone. The proposed models show U10 estimation up to 35 ms-1 with 1 ms-1 accuracy and major improvement inside the tropical cyclone rain and at the high wind speed regime. This too shows the ability of satellite altimeter in estimating U10 in extreme environment with great accuracy. [ABSTRACT FROM AUTHOR]

In comparison with seasonal sea ice (first-year ice, FY ice), multiyear (MY) sea ice is thicker and has more opportunity to survive through the summer melting seasons. Therefore, the variability of wintertime MY ice plays a vital role in modulating the variations in the Arctic sea ice minimum extent during the following summer. As a response, the ice-ocean-atmosphere interactions may be significantly affected by the variations in the MY ice cover. Satellite observations are characterized by their capability to capture the spatiotemporal changes of Arctic sea ice. During the recent decades, many active and passive sensors onboard a variety of satellites (QuikSCAT, ASCAT, SSMIS, ICESat, CryoSat-2, etc.) have been used to monitor the dramatic loss of Arctic MY ice. The main objective of this study is to outline the advances and remaining challenges in monitoring the MY ice changes through the utilization of multiple satellite observations. We summarize the primary satellite data sources that are used to identify MY ice. The methodology to classify MY ice and derive MY ice concentration is reviewed. The interannual variability and trends in the MY ice time series in terms of coverage, thickness, volume, and age composition are evaluated. The potential causes associated with the observed Arctic MY ice loss are outlined, which are primarily related to the export and melting mechanisms. In addition, the causes to the MY ice depletion from the perspective of the oceanic water inflow from Pacific and Atlantic Oceans and the water vapor intrusion, as well as the roles of synoptic weather, are analyzed. The remaining challenges and possible upcoming research subjects in detecting the rapidly changing Arctic MY ice using the combined application of multisource remote sensing techniques are discussed. Moreover, some suggestions for the future application of satellite observations on the investigations of MY ice cover changes are proposed. [ABSTRACT FROM AUTHOR]

Using Argo observations and Estimating the Circulation and Climate of the Ocean data sets, this study investigates the sea surface salinity (SSS) variability and its relationship with ocean dynamics in the southwestern tropical Indian Ocean (SWTIO) associated with the 2010 negative Indian Ocean dipole (IOD) event. The results show that the ocean circulation in the tropical southern Indian Ocean (IO) significantly contributes to the SSS anomalies during the evolution of the negative IOD event. The anomalous eastward current advected the high‐salinity water into the eastern equatorial IO during July–October 2010. Then the positive SSS anomalies expanded southward to 6–8°S due to the southeastward mean seasonal currents in the eastern equatorial IO during November–December 2010. A salinity budget analysis has been used to identify key processes in contributing to the SSS variations in the SWTIO. The decreased precipitation in the western and central equatorial IO leads to high SSS anomalies from January to April 2011. Then the anomalous southwestward currents transport the higher SSS water from the eastern equatorial IO to the SWTIO until May–June 2011. At the same time, the upwelling Rossby waves shoal the thermocline and mixed layer depth, bringing high‐salinity subsurface water to the surface layer and cooling the sea surface temperature, which further depresses local precipitation to provide a positive feedback for the SSS increase. Key Points: The horizontal advection dominates the SSS variation during the developing and mature phases of the IOD eventsLocal rainfall and the SEC advection contribute to the positive SSS anomalies in the southwestern tropical Indian OceanUpwelling Rossby waves shoal thermocline and enhance the positive SSS anomalies [ABSTRACT FROM AUTHOR]

A new model for the M2, S2, K1, and O1 tides in the Weddell Sea is developed by assimilating CryoSat‐2 data into a barotropic tide model. A variational approach is used, which explicitly allows for errors in the water depth, that is, the bottom topography in open water and the water column thickness under floating ice shelves, so that an optimized estimate of the topography is obtained together with the tidal fields. In preparation for assimilation, the sensitivity of the tidal elevation to the interfacial drag at the sea floor and the ice‐water interface (under the floating ice shelves) is investigated; this motivates the development of a new drag parameterization which is more accurate and physically plausible in comparison with the interfacial drag alone. The assimilation of CryoSat‐2 data into the model results in tidal elevations with essentially the same accuracy as previous estimates, which is demonstrated by comparisons with independent in situ data and withheld CryoSat‐2 data. The novelty of the present tidal estimates is that they are consistent with well‐defined dynamics based on the Laplace Tidal Equations—augmented with the new parameterization of drag—and modifications of the prior estimate of underwater topography and water column thickness. Analysis of the sensitivity to the topography finds that, at this level of precision, the topography is not uniquely determined by the observed data. Key Points: A new model for the M2, S2, K1, and O1 barotropic tides in the Weddell Sea is developed from CryoSat‐2 dataThe tidal dynamics are assumed to follow a generalization of the Laplace tidal equations which uses a new parameterization of dissipationVariational assimilation is used to estimate tidal fields, ocean bottom topography, and water column thickness under floating ice shelves [ABSTRACT FROM AUTHOR]

Large‐scale spatial and temporal variabilities of sea surface salinity (SSS) in the Southern Ocean from 2011 to 2017 were studied using products derived from microwave sensors on board Aquarius, Soil Moisture and Ocean Salinity (SMOS), and Soil Moisture Active and Passive (SMAP) satellites. Four products, three from Aquarius and one from SMOS, were evaluated and shown to be generally consistent within 0.3 to 0.6 psu and agree favorably with in situ measurements. However, although the Aquarius products show consistent seasonality of SSS with high values of 34.45 psu in October and low values of 33.40 psu in May, the SMOS and SMAP products lack such seasonal variations. This may be caused by larger uncertainties in the SMOS and SMAP data due in part to the lack of concurrent scatterometer measurements that is used to correct for roughness effects. The four products provide similar spatial distributions of SSS with root‐mean‐square difference from 0.25 to 0.58 psu. Differences among Aquarius products are mainly due to varying salinity retrieval algorithms, smoothing, and masking of sea ice, while the SMOS product showed the highest SSS deviation that is likely due to the bias‐adjustment done on the data set. Our analyses show that SSS in the Southern Ocean region has significant meridional variations with the lowest SSS near the ice edge and highest at lower latitudes. The SSS is also lowest in summer indicating the predominant influence of sea ice and glacial melt, but it stays low near ice edges even during the growth season. Plain Language Summary: Salinity together with temperature is the key parameters that control the state and circulation of the World's oceans. The large‐scale distribution of the sea surface salinity of the Southern Ocean is quantified for the first time using Aquarius, Soil Moisture and Ocean Salinity, and Soil Moisture Active and Passive satellite microwave data. Seasonal and interannual changes in the distribution as affected by the sea ice cover, surface temperature, and precipitation are evaluated. Comparative studies were done, using four different products that are publicly available, in conjunction with in situ observations to gain insights into the true nature of the distribution and how consistently the sea surface salinity is depicted by the different products. There are general consistencies in the products, and discrepancies are attributed to different algorithms, smoothing techniques, and sea ice masking. Aquarius data are shown to have higher accuracy than Soil Moisture and Ocean Salinity and Soil Moisture Active and Passive products in part because of having concurrent scatterometer that provides accurate correction to roughness effects. Key Points: Spatial and temporal variabilities of SSS in the Southern Ocean were quantified using four different SSS productsValidation studies show good agreement of situ data with satellite SSS data with RMSD varying from 0.25 to 0.58 psuObserved seasonal and interannual changes agree with expected changes associated with sea ice, precipitation and polar fronts [ABSTRACT FROM AUTHOR]

The current popular GNSS RTK technique would be not applicable on ocean due to the limited communication access for transmitting differential corrections. A new technique is proposed for high-precision ocean RTK, referred to as ORTK, where the corrections are transmitted by employing the function of BeiDou satellite short-message communication (SMC). To overcome the limitation of narrow bandwidth of BeiDou SMC, a new strategy of simplifying and encoding corrections is proposed instead of standard differential corrections, which reduces the single-epoch corrections from more than 1000 to less than 300 bytes. To solve the problems of correction delays, cycle slips, blunders and abnormal epochs over ultra-long baseline ORTK, a series of powerful algorithms were designed at the user-end software for achieving the stable and precise kinematic solutions on far ocean applications. The results from two long baselines of 240 and 420 km and real ocean experiments reveal that the kinematic solutions with horizontal accuracy of 5 cm and vertical accuracy of better than 15 cm are achievable by convergence time of 3-10 min. Compared to commercial ocean PPP with satellite telecommunication, ORTK is of much cheaper expense, higher accuracy and shorter convergence. It will be very prospective in many location-based ocean services. [ABSTRACT FROM AUTHOR]

The TOPEX/POSEIDON satellite mission to observe the oceans triggered the formation of the new specialty of space oceanography from the 1970s to 1990s. Previously, in the 1960s in the United States, traditional oceanographers had shown little interest in the possibilities of space and thus space engineers and physicists worked on the first missions (Seasat in particular). TOPEX/POSEIDON brought together two projects, one American (TOPEX) and the other French (POSEIDON). The gradual crystallization of the disciplinary specialty of space oceanography occurred by making available a platform of instruments able to meet an ensemble of varied needs. Battery failures just before the launch of the joint mission meant that the mission had to focus on the essentials (notably El Niño effects). Subsequently, the discovery of a significant rise in sea levels due to global warming resulted in space oceanography becoming a recognized specialty. The case of TOPEX/POSEIDON shows the original ways in which instruments gained a place in the very large range of oceanographic techniques. [ABSTRACT FROM AUTHOR]

Collecting AIS messages from ships by satellites allows for maritime situational awareness, and a wide range of commercial applications, at global and regional scales. This work provides methods and indicators for evaluation of the maritime picture in terms of completeness as well as update intervals of ship tracks. The distribution of the maximum daily time gap between messages of each ship gives good understanding of the freshness of the maritime picture. The distribution is however very skewed, and therefore not well described by the mean and standard deviation. As a single indicator, the median value gives a description of the typical quality of service, whereas percentile levels give insight in the spread. The data used were collected in August 2015 in the Eastern and Southern Africa/Indian Ocean region. Four providers of satellite AIS data were used, plus coastal AIS, making the data set one of the most complete available. Typically 575,000 AIS messages from 1630 ships were received per day. The median value of the longest time gap in ship tracks was 4.3 h; and the 70- and 90-percentiles were 6.7 h and 19.5 h, respectively. When subsets of all data are used, starting with the data from one provider and adding the others one by one, it is found that the completeness increases asymptotically, but the median of the maximum daily time gap keeps decreasing linearly, showing that additional data in the first place help to track the ships that are already known. [ABSTRACT FROM AUTHOR]

Satellite remote sensing has provided an unprecedented opportunity to understand the spatio-temporal change of the Earth’s climate system. In this study, we take advantage of the oceanographic satellite-based data to examine the global mean sea level rise, with a focus on a transitional episode (1994-2003) referred to as the onset of recent global warming hiatus. We remove the signals accounted for the El Niño-Southern Oscillation, the Pacific Decadal Oscillation, and solar radiation using an Empirical Orthogonal Function and multivariate regression analysis. The trend estimates over the period 1993-2015 are significantly improved in accordance with the reduction of uncertainty by half. Our results associate the observed deceleration of sea level rise during the onset with the climate oscillations. It strengthens a conclusion deduced by an alternative approach using modelling, whilst highlights the robustness of combining satellite-based datasets and climate indices in a reliable statistical estimation. [ABSTRACT FROM AUTHOR]

Widespread short-period internal wave (SPIW) activity in the White Sea has been revealed for the first time based on long-term (2009-2013) monitoring performed using satellite and in situ observations, and the statistical characteristics of these waves have been obtained. Two main regions where short-period waves constantly exist have been identified: the shelf area near the frontal zone at the boundary between the Basin and the Gorlo Strait and the shallow shelf area where the depths are about 30-50 m near Solovetskie Islands. Intense internal waves (IIWs), which are substantially nonlinear and are related to specific phases of a barotropic tide, are regularly observed near frontal zones. The wave height can reach half the sea depth and the wave periods vary from 7 to 18 min. [ABSTRACT FROM AUTHOR]

Marine processes are observed with sensors from both the ground and space over large spatio-temporal scales. Citizen-based contributions can fill observational gaps and increase environmental stewardship amongst the public. For this purpose, tools and methods for citizen science need to (1) complement existing datasets; and (2) be affordable, while appealing to different user and developer groups. In this article, tools and methods developed in the 7th Framework Programme of European Union (EU FP 7) funded project Citclops (citizens' observatories for coast and ocean optical monitoring) are reviewed. Tools range from a stand-alone smartphone app to devices with Arduino and 3-D printing, and hence are attractive to a diversity of users; from the general public to more specified maker- and open labware movements. Standardization to common water quality parameters and methods allows long-term storage in regular marine data repositories, such as SeaDataNet and EMODnet, thereby providing open data access. Due to the given intercomparability to existing remote sensing datasets, these tools are ready to complement the marine datapool. In the future, such combined satellite and citizen observations may set measurements by the engaged public in a larger context and hence increase their individual meaning. In a wider sense, a synoptic use can support research, management authorities, and societies at large. [ABSTRACT FROM AUTHOR]

A new database of ocean wave parameters has been created based on satellite altimetry observations. The basis was data from the European Space Agency project GlobWave (www.globwave.org), which was transformed to suit upcoming requirements for global wave analysis. The new database contains additional wave characteristics (altimetry wind speed estimated using different parametric models, steepness, period, and some quality control parameters). It provides up-to-date tools for mass data preprocessing. The new database makes it possible to optimize wave field diagnostics on regional and global scales. Using the Envisat and Jason-1 satellite missions as an the example, we demonstrate the specific features of using the initial GlobalWave data set and the modified database. [ABSTRACT FROM AUTHOR]

The seasonal variations of the Kuroshio intrusion pathways northeast of Taiwan were investigated using observational data from satellite-tracked sea surface drifters and a numerical particle-tracking experiment based on a high-resolution numerical ocean model. The results of sea surface drifter data observed from 1989 to 2013 indicate that the Kuroshio surface intrusion follows two distinct pathways: one is a northwestward intrusion along the northern coast of Taiwan Island, and the other is a direct intrusion near the turn of the shelf break. The former occurs primarily in the winter, while the latter exists year round. A particle-tracking experiment in the high-resolution numerical model reproduces the two observed intrusion paths by the sea surface drifters. The three-dimensional structure of the Kuroshio intrusion is revealed by the model results. The pathways, features and possible dynamic mechanisms of the subsurface intrusion are also discussed. [ABSTRACT FROM AUTHOR]

Uncertainties in the satellite-derived surface skin temperature (SST) data in the polar oceans during two periods (16-24 April and 15-23 September) 2003-2014 were investigated and the three data sets were intercompared as follows: MODerate Resolution Imaging Spectroradiometer Ice Surface Temperature (MODIS IST), the SST of the Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit-A (AIRS/AMSU), and AIRS only. The AIRS only algorithm was developed in preparation for the degradation of the AMSU-A. MODIS IST was systematically warmer up to 1.65K at the sea ice boundary and colder down to -2.04K in the polar sea ice regions of both the Arctic and Antarctic than that of the AIRS/AMSU. This difference in the results could have been caused by the surface classification method. The spatial correlation coefficient of the AIRS only to the AIRS/AMSU (0.992-0.999) method was greater than that of the MODIS IST to the AIRS/AMSU (0.968-0.994). The SST of the AIRS only compared to that of the AIRS/AMSU had a bias of 0.168K with a RMSE of 0.590K over the Northern Hemisphere high latitudes and a bias of -0.109K with a RMSE of 0.852K over the Southern Hemisphere high latitudes. There was a systematic disagreement between the AIRS retrievals at the boundary of the sea ice, because the AIRS only algorithm utilized a less accurate GCM forecast over the seasonally varying frozen oceans than the microwave data. The three data sets (MODIS, AIRS/AMSU and AIRS only) showed significant warming rates (2.3±1.7~2.8±1.9 K decade-1) in the northern high regions (70-80° N) as expected from the icealbedo feedback. The systematic temperature disagreement associated with surface type classification had an impact on the resulting temperature trends. [ABSTRACT FROM AUTHOR]

Nowadays, data combination/fusion is a common practice to integrate multiple data sources into a spatially and/or temporally regular data set for facilitating analysis and interpretation. Given the advancement in active remote sensing for monitoring our changing environment (no matter ocean, land or ice), the data acquisition from various spaceborne platforms with different spatio-temporal resolutions is enormous; calling for a need of multisatellite data combination. Instead of equally or spatially weighted solution, this article illustrates a spatio-temporal combination approach that weights data both in space and in time simultaneously for ocean tide modelling using multisatellite altimetry data sets under different spatial and temporal resolutions. The tide models generated from this approach show substantial improvement near coastal regions when compared to other contemporary ocean tide models by using independent pelagic and coastal tide gauges serving as ground truth. The discrepancy of the best model is ~23%, three times larger than that of the deep ocean. Further improvement lies in more and better spatio-temporal observations in the near future. We anticipate this approach can be applied to other spatio-temporal data in a similar settings for spatio-temporal dependent unknown parameters, including geodetic, geophysical, oceanographic data and imagery under different spatial and temporal resolutions. [ABSTRACT FROM AUTHOR]

Massive amounts of anthropogenic radiocaesium 137Cs that was released into the environment by the Fukushima Dai-ichi Nuclear Power Plant accident on March 2011 are widely known to have extensively migrated to Pacific oceanic sediment off of east Japan. Several recent reports have stated that the sedimentary 137 Cs is now stable with a remarkably heterogeneous distribution. The present study elucidates ocean dynamic processes causing this heterogeneous sedimentary 137Cs distribution in and around the shelf off Fukushima and adjacent prefectures. We performed a numerical simulation of oceanic 137Cs behaviour for about 10 months after the accident, using a comprehensive dynamic model involving advection-diffusion transport in seawater, adsorption and desorption to and from particulate matter, sedimentation and suspension on and from the bottom, and vertical diffusion transport in the sediment. A notable simulated result was that the sedimentary 137Cs significantly accumulated in a swath just offshore of the shelf break (along the 50-100m isobath) as in recent observations, although the seabed in the entire simulation domain was assumed to have ideal properties such as identical bulk density, uniform porosity, and aggregation of particles with a single grain diameter. This result indicated that the heterogeneous sedimentary 137Cs distribution was not necessarily a result of the spatial distribution of 137Cs sediment adsorptivity. The present simulation suggests that the shape of the swath is mainly associated with spatiotemporal variation between bottom shear stress in the shallow shelf (< 50m depths) and that offshore of the shelf break. In a large part of the shallow shelf, the simulation indicated that strong bottom friction suspending particulate matter from the seabed frequently occurred via a periodic spring tide about every 2 weeks and via occasional strong wind. The sedimentary 137Cs thereby could hardly stay on the surface of the seabed with the result that the simulated sedimentsurface 137Cs activity tended to decrease steadily for a long term after the initial 137Cs migration. By contrast, in the offshore region, neither the spring tide nor the strong wind caused bottom disturbance. Hence, the particulate matter incorporated with 137Cs, which was horizontally transported from the adjacent shallow shelf, readily settled and remained on the surface of the sediment just offshore of the shelf break. The present simulation also clearly demonstrated that the bottom disturbance influenced the sedimentary 137Cs distributions not only horizontally but also vertically. In particular, within a part of the near-shore off the nuclear power plant, the simulation indicated that large amounts of the sedimentary 137Cs were present in both upper and deeper sediments. As a result, total sedimentary 137Cs in the entire simulation domain (1.4×105 km²) at the end of 2011 was 3.2×1015 Bq, more than 10 times that in previous estimates using samples of upper sediments. [ABSTRACT FROM AUTHOR]

SARAL/AltiKa surface wind speed (WS) and significant wave height (SWH) measurements are monitored and validated against operational European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric and wave model results in addition to available in-situ observations to access their suitability for various applications, especially SWH data assimilation. The quality of SWH is very high while that of WS is very good except for an underestimation of high wind speeds. The impact of assimilating SWH in the ECMWF Integrated Forecast System was assessed using several numerical experiments. The results show positive impact. Operational assimilation of SWH at ECMWF model is part of the forthcoming model change. [ABSTRACT FROM PUBLISHER]

The current mean sea level (MSL) continuous record, essential for the understanding of climate evolution, is computed with the altimetric measurements of the TOPEX/Poseidon mission, succeeded by Jason-1 and later Jason-2. The accurate continuity of the record is ensured by the conservation of the "historical" TOPEX orbit, but also by calibration phases between the successive missions which enable a rigorous computation of their relative biases. In order to extend the current MSL record, Jason-3 will be the natural successor of Jason-2: on the same orbit with a calibration phase. Shortly after Jason-3, another altimetric climate-oriented mission, Sentinel-3a, will be launched on a different orbit. In this paper, simulated altimetric sea level data is used to study the sensitivity of the MSL continuous record to the change of the "historical" orbit for the new Sentinel-3a orbit. By estimating the impact of the absence of calibration phase on the MSL continuous record trend accuracy at global and regional scale and the impact of the orbit change on the long-term continuity of this MSL record, this study shows that linking Sentinel-3a data instead of Jason-3 to the MSL continuous record would prevent from meeting climate users requirements regarding the MSL trend accuracy. [ABSTRACT FROM AUTHOR]

The location of tide gauges is not random. If their locations are positively (negatively) correlated with sea level rise (SLR), estimates of global SLR will be biased upwards (downwards). Using individual tide gauges obtained from the Permanent Service for Mean Sea Level during 1807-2010, we show that tide gauge locations in 2000 were independent of SLR as measured by satellite altimetry. Therefore these tide gauges constitute a quasi-random sample, and inferences about global SLR obtained from them are unbiased. Using recently developed methods for nonstationary time series, we find that sea levels rose in 7 % of tide gauge locations and fell in 4 %. The global mean increase is 0.39-1.03 mm/year. However, the mean increase for locations where sea levels are rising is 3.55-4.42 mm/year. These findings are much lower than estimates of global sea level (2.2 mm/year) reported in the literature and adopted by IPCC (), and which make widespread use of imputed data for locations which do not have tide gauges. We show that although tide gauge locations in 2000 are uncorrelated with SLR, the global diffusion of tide gauges during the 20th century was negatively correlated with SLR. This phenomenon induces positive imputation bias in estimates of global mean sea levels because tide gauges installed in the 19th century happened to be in locations where sea levels happened to be rising. [ABSTRACT FROM AUTHOR]

The availability of light in the ocean is an important parameter for the determination of phytoplankton photosynthesis processes and primary production from satellite data. It is also a useful parameter for other applications, e.g. the determination of heat fluxes. In this study, a method was developed utilising the vibrational Raman scattering (VRS) effect of water molecules to determine the amount of photons available in the ocean water, which is expressed by the depth integrated scalar irradiance Ē0. Radiative transfer simulations with the fully coupled ocean-atmosphere Radiative Transfer Model (RTM) SCIATRAN show clearly the relationship of Ē0 to the strength of the VRS signal measured at the top of the atmosphere (TOA). Taking advantage of VRS structures in hyper-spectral satellite measurements a retrieval technique to derive Ē0 in the wavelength region from 390 to 444.5 nm was developed. This approach uses the Weighting Function Differential Optical Absorption Spectroscopy (WF-DOAS) technique, applied to TOA radiances, measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Based on the approach of Vountas et al. (2007), where the DOAS method was used to fit modelled spectra of VRS, the method was improved by using the weighting function of VRS (VRS-WF) in the DOAS fit. This was combined with a look-up table (LUT) technique, where the Ē0 value was obtained for each VRS satellite fit directly. The VRS-WF and the LUT were derived from calculations with the RTM SCIATRAN (Rozanov et al., 2014). RTM simulations for different chlorophyll a concentrations and illumination conditions clearly show, that low fit factors of VRS retrieval results correspond to low amounts of light in the water column and vice versa. Exemplary, one month of SCIAMACHY data were processed and a global map of the depth integrated scalar irradiance Ē0 was retrieved. Spectral structures of VRS were clearly identified in the radiance measurements of SCIAMACHY. The fitting approach led to consistent results and the WF-DOAS algorithm results of VRS correlated clearly with the chlorophyll concentration in case-I water. Comparisons of the di use attenuation coefficient, extracted by VRS fit results, with the established GlobColour Kd(490) product show consistent results. [ABSTRACT FROM AUTHOR]

The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A) and the Visible/Infrared Imager/Radiometer Suite (VIIRS), is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the Ocean Color component of the Aerosol Robotic Network (AERONET-OC). The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities with those observed at the Gloria site. Results from the comparison of normalized-water leaving radiance LWN indicate biases of a few percent between satellite derived and in situ data at the center-wavelengths relevant for the determination of chlorophyll a concentration (443-547 nm, or equivalent). Remarkable is the consistency among the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center-wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm) and red (i.e., 667 nm, or equivalent) center-wavelengths, suggesting difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters. [ABSTRACT FROM AUTHOR]